In a photomechanical process, a photographic images having a continuous tone are converted into so-called halftone dot images of the shade of the continuous tone images expressed by the sizes of varying halftone dot areas and an original for printing is made by combining the halftone dot images with another original having letter images and line images.
For reproducing good line images or halftone dot images, a photographic light-sensitive material, which is used for a photomechanical process is required to show so-called high contrast (in particular, of higher than 10 in gamma) photographic characteristics having a high image contrast and high blackened density clearly distinguishing image portions and non-image portions.
Hitherto, for the aforesaid purpose, a method of processing a so-called lithographic type silver halide light-sensitive material composed of silver chlorobromide containing less than 40 mol % silver bromide with a hydroquinone developer (lithographic developer) having a very low effective concentration (usually, lower than 0.1 mol/liter) of sulfite ion is generally employed. However, since in this method the concentration of sulfite ion in the developer is low, the developer is very unstable to air oxidation.
Accordingly, an image-forming system of developing the light-sensitive material with a processing solution having a good storage stability for eliminating the unstability of the image formation by the lithographic development to provide a high contrast photographic characteristic has been desired. A system of forming a negative image having a high contrast of over 10 in gamma by processing a surface latent image type silver halide photographic material containing a specific acylhydrazine compound with a developer of 10.5 to 12.3 pH containing a sulfite preservative of higher than 0.15 mol/liter and showing a good storage stability has been proposed, for example, in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, 4,311,781, etc. The new image forming system has a feature that silver iodobromide or silver chloroiodide having high sensitivity can be used while in a silver chloride or silver chlorobromide only can be used.
For a silver halide photographic material are frequently used water-soluble dyes for various purposes such as safe light adaptability, etc. In particular, for enabling the contact printing step in a photomechanical process under a bright safe light, it has been attempted to reduce the sensitivity of a silver halide emulsion by using an inorganic or organic desensitizer such as a rhodium salt, an iridium salt, pinakryptol yellow, phenosafranine, etc., and at the same time, to add a safe light dye to the silver halide emulsion. On the other hand, it has been found that the addition of such a dye to a silver halide emulsion sometimes loses the controllability of the letter line width and the tone controllability of the halftone dot images in the contact printing step in a photomechanical process (practically, a performance capable of increasing the width to some extent more than the letter line width of the original used and broadening to some extent the areas of the halftone dots more than those of the original halftone dots, a performance capable of making such a correction of the original in the case of giving an artisitic impression being required in addition to the performance capable of reproducing completely the same line width and dot area as those of the original in the contact printing step) and also as well as reduces the contrast increasingly effect by the aforesaid hydrazone derivative.